Compartmented spray devices, wherein certain spraying compartments are separated by a movable piston, are generally well known. (See, e.g., U.S. Pat. No. 1,030,119 to Overbeke.) Many sprayer devices of this kind often present certain problems in operation and, as a result, greater sophistication or complexity in design is often deemed warranted. Greater complexity in design, however, typically gives rise to greater complexity in operation. (See, in particular, U.S. Pat. No. 1,117,228, also to Overbeke; and see U.S. Pat. No. 1,241,551 to Preston et al.; U.S. Pat. No. 1,347,520 to Rasch; U.S. Pat. No. 3,217,936 to Abplanalp; U.S. Pat. No. 3,225,759 to Drapen et al.; and U.S. Pat. Nos. 4,406,406 and 4,545,535, both to Knapp.)
Fluid dispensing systems that are particularly designed to internally mix ingredients are similarly well known. (See, e.g., U.S. Pat. No. 368,259 to Warren; and U.S. Pat. Nos. 4,406,406 and 4,545,535, both to Knapp.) For a number of reasons, however, it is desirable to mix ingredients external to the dispensing system. In particular, reliance upon a dispensing system that internally mixes ingredients can, in certain situations, lead to undesired contamination of a pure ingredient source that is in fluid communication with the internally-mixed ingredients of such a dispensing system.
Also well known are prior-art fluid dispensing systems that externally mix ingredients (which are to be dispensed). Many dispensing systems of this type, unfortunately, are rather complex in design and/or operation, with the result being that the overall effectiveness or utility of each such dispensing system is generally uniquely encumbered by the complexity of its own design. (See, e.g., U.S. Pat. No. 1,347,520 to Rasch; U.S. Pat. No. 1,370,687 to Ferris; U.S. Pat. No. 1,590,430 to Erby; and U.S. Pat. No. 1,948,533 to Neely.) In particular, U.S. Pat. No. 1,948,533 to Neely discloses one such spraying device that is complex not only in design but also in operation.
While some prior-art piston-powered dispensing systems--such as that system disclosed in U.S. Pat. No. 2,708,600 to Froidevaux, which features external-mixing of ingredients--tout an apparent simplicity-of-design feature, many practical applications that utilize such a fluid dispensing system require inclusion of certain structural details (absent from the dispensing system disclosed by Froidevaux) which, if present, would render complex the overall dispensing system, in design and/or in operation.
In light of the sophisticated and critical nature of many of today's consumers, simplicity of design, effectiveness of operation, and overall convenience to the user, are highly desirable features or aspects of any fluid-dispensing system.